Hydraulics 1 Flashcards
Advantages of hydraulic systems
weight action maintenance and efficient
Disadvantages of hydraulics systems
Leakage and contamination
applied to a liquid causes liquid to expand and exert pressure
heat
transmitted undiminished in all directions
pressure
3 basic principles
force pressure and working area
exerted in pounds
force
exerted in pounds per square inch
pressure
expressed in square inches
working area
pressure exerted on an enclosed liquid is transmitted equally and undiminished in all directions and acts with equal force on all areas
pascal’s law
MARCH
Manual bypass valve Actuating cylinder Reservoir Check valves Hand pump
located in the return line stops fluid when closed
Manual bypass valve
receives fluid pressure and transforms linear mechanical motion
Actuating cylinder
tank that holds the supply of fluid
reservoir
unit creates flow of fluid
hand pump
allows fluid flow in one direction only
check valves
the presence of undesirable foreign matter that may or may not be visible to the unaided eye
hydraulic fluid contamination
to achieve and maintain a satisfactory level of purity in hydraulic systems thereby providing for the safe efficient operation of naval aircraft and support equipment
hydraulic fluid contamination control program
particulate contamination may result from internal wear and failure of system components, maintenance malpractice, or poorly maintained support equipment
contamination sources
2 classifications of contamination
particulate and fluid
principle causes if wear in hydraulic pumps, actuators, valve, and servo valves
particulate contamination
3 parts of particulate contamination
organic solids
metallic solids
inorganic solids
4 types of fluid contamination
air
water
solvent
foreign
may be introduced through improper maintenance or a result of system design. can cause fire inside
air
adversely affect by dissolved, emulsified, or free water. separates from fluid and collects in filter bowls, and other critical locations
water
is a special form of foreign fluid contamination in which the original contaminating substance is a chlorinated solvent
solvent
generally the result of lube oil, engine, fuel, or incorrect hydraulic hydraulic fluid having been introduced inadvertently into the system during servicing
foreign
output greater than input required
mechanical advantage
Hydraulic system
sharp
SHARP
Selector valve Hydraulic lines Actuating cylinder Reservoir Pump
hold supply fluid
provide space for thermal expansion
provide a means for bleeding air
Reservoir
create flow of fluid
draw fluid from the reservoir and send it out the system
primarily source of hydraulic power
Pump
to direct flow of fluid to and from actuating units
Selector valve
converts fluid energy into linear mechanical motion
actuating cylinders
converts hydraulic pressure into rotary mechanical motion
hydraulic cylinders
the medium for transmitting the fluid from one component to another
hydraulic lines
to protect internal parts of the cage from damage due to shocks and surges in the system
snubber
Fluid Characteristics
low viscosity
lubricating qualities
corrosion stability
viscosity is the resistance of a fluid to flow. viscosity of hydraulic fluid should be low and constant
low viscosity
the units in a hydraulic system are self-lubricated by the fluid flowing through them. it is necessary that the fluid has good lubrication qualities
lubricating qualities
hydraulic fluid must resist oxidation and inhibit corrosion
corrosion stability
to transmit energy
fluid
are used in naval aircraft and ground support equipement
synthetic based fluids
primary fluid fire-resistant type of fluid
MIL-PRF-83282
primarily used as a preservative for a hydraulic system in storage
MIL-H-46170
is to hold a supply of fluid for the system
reservoir
are not adapted to high-altitude flight or violent manuvers
non-pressurized
made of corrosion resistant metal and has a filler neck to provide a means of filling the reservoir with fluid
filler neck and housing
return port and the pump supply port
ports
inside of the tank in such a manner as to clean all returning fluid
filter
to prevent fluid flowing directly from the return line to the outlet of the pump and also to reduce surging and vortexing
baffle
electronic particle counter are the preferred method for measuring particle contamination
particle counters
size of the particulate matter in hydraulic fluid is measured in
microns
alternate method to measure hydraulic fluid contamination
patch testing
is to remove foreign matter from the contaminated fluid itself
decontamination method
four basic methods
re-circulation cleaning
purifying
flushing
purging
to create a flow of fluid
location is determined by its source of power
hydraulic pump
Pump displaces the same quantity of fluid on each revolution
Constant displacement pump
Pump contains it’s own regulating device and can change pump displacement to meet the needs of the system
Variable displacement
A constant displacement pump that consist of two mashed years, which revolve in a housing. One gear is driven by the driveshaft, the other is a driven gear
Gear pump
Hand pump, double action pump, Vickers seven piston, and Vickers nine-piston
Piston pump’s
Provides an emergency means of operating hydraulic units in the event of failure of the main pump, through two check valves
Hand pump
Discharges fluid to the line of backstroke and forward stroke
Double action pump
Is a constant displacement pump that consist of a housing, a rotating group, and a valve plate
Vickers seven piston
Is a variable displacement pump that consist of a housing, a rotating group, a valve plate, a yoke, and a pressure control assembly
Vickers nine piston
Pump repair I level replacement of gaskets o level
Maintenance
To prevent damage to the power source of the pump in the event of the pump binding
Shear shaft
Allows the reservoir to breathe
Vent line
To show the fluid level in a reservoir
Fluid level indicators
Ensure a constant fluid flow to the pump
Pressurized reservoir
Regulator maintains a constant air pressure
Air fluid separated
Can be installed anywhere before the pump and a hydraulic system
pressurized reservoir
Is a primary concern is servicing hydraulic reservoir’s
Cleanliness
Is located on or near reservoir that contains the following detailed info necessary. Fluid type, reservoir capacity, and caution notes
A plachr or Information plate
To protect the hydraulic system from damage that could result from excessive pressure, caused by failure of the pump regulating devices, thermal expansion, and pressure surges
Hydraulic relief valves
Relieve excessive pressure caused by thermal expansion
Thermal relief valves
To protect the hydraulic system from excessive pressure by releasing hydraulic fluid from the pressure line into the return line
Main system relief valves
The inlet and outlet bodies are threaded together around the valve sleeve
Housing
A finish surface and acts as the cylinder chamber for the piston
Valve sleeve
Contains the poppet valve that consist of the poppet, poppet Spring, cage, and adjusting nut
Inlet body
Contains the spigot, load spring, and piston
Outlet body
When the pressure of the hydraulic system reaches the opening pressure setting, and fluid flows through the valve into the return line
Opening
When the pressure of the hydraulic system drops to the receding pressure and fluid flow through the valve ceases
closing
When the pressure at the outlet port exceeds the pressure at the end report and fluid will flow to the pressure line
Free reverse valve
On relief valves is limited to checking the valves for external leaks, proper relieving pressure if a relief valve failed to operate properly. Must be replaced
Maintenance
Three parts of a hydraulic filter
Head assembly, filter element, and bowl
Is to filter the fluid of the hydraulic system of foreign particles and contaminative substances
Hydraulic filters
Nearest element in use, made of organic and inorganic fibers, bonded by proxy resin, with a metal screen on both sides to protect the system. 1 to 10 microns
5 micron disposable filter
Made of stainless steel wire mash, can be cleaned and reused. 15 to 25 µm
Stainless steel filter
Made of chemically treated paper formed in convolutions, or accordion please, to increase filter capability. 10 to 20 µm
Micronic filter
Consist of Minuet bronze balls join together as one piece, but still remaining porous. 25 microns
Sintered filter
Provides information on servicing filters of aircraft hydraulic systems
Maintenance instructions manual
Provides inspection information and changing intervals of filters
Maintenance requirements cards
Provides cleaning and testing information for filter elements
Aviation hydraulics manual
Made only at I level
Adjustments
Check for proper operation and check for external leakage
Installing
Ensure that the pressure in the hydraulic system has been relieved
Removal
To store hydraulic fluid under pressure for normal and emergency use
Hydraulic accumulators
Aid pump at peak low demand
Normal
If the pressure of the main system is lost, fluid that is stored under pressure in an accumulator of a sub system maybe used to actuate that subsystem
Emergency
Absorbs shock and surges of fluid within plants and absorbs thermal expansion
Function
Pressure line, screen disc, fluid chamber, diaphragm, nitrogen chamber, air valve cap
Spherical or diaphragm
Chromium plated on inside end cap , fluid port, Barrel , piston, O-ring package and back up ring, and nitrogen port
Cylindrical or piston
React to changes in the fluid pressure of the system
Accumulators
Referred to ____To determine proper preload of the accumulator, standard removal or installation procedures, and other important instructions
Maintenance Instruction manual
To reduce the pressure of the main system to a predetermined lower pressure in the subsystem
Pressure reducing valve
Any pressure alarm of the main system just prior to the pressure line of the subsystem
Location of the pressure reducing valve
Body and ports, sleeve and Shuttle assembly, relief valve spring, and a cap
Components of a pressure reducing valve
Retaining flange, o ring gaskets, and sleeve holes
Sleeve
Inner bore, seat, metering groove, Shuttle holes
Shuttle
Determines the amount of reduced pressure in the subsystem
Relief valve spring
Screws onto the body and hold the relief valve spring in the housing and an adjustment screw is Incorporated in the cap
Cap
The shuttle is held in the unseeded position by the relief valve spring
Open position of the pressure reducing valve
When pressure in the subsystem reaches its setting, the relief valve spring is over come
Balanced position of the pressure reducing valve
Nitrogen pressure in an accumulator
Preloading
Examine accumulators for external and fluid nitrogen leaks detect nitrogen leaks by brushing with soapy water, loosen air valves to check for internal leaks
Inspection
The majority of accumulators enable aircraft are equipped with a gauge to check the preload
Pressure gauge method
If the pressure of the subsystem becomes too great, the relief valve springs should be compressed further by the shuttle, and excessive pressure will be relieved by allowing fluid to be routed to the return port will relieve excessive pressure
Relief flow operation
Referred to maintenance instruction manual if pressure reducing valve operates in properly
Maintenance
Hydraulic system pressure must be the depressurized
Safety precautions
Is to direct a fluid fluid to and from the actuating cylinder
Solenoid operated selector valve
Body, sleeve, slide
Components of a solenoid operated selector valve
Cast aluminum alloy that contains four fluid ports; pressure, return, and two cylinders
Body
Hollow still sleeve inserted into the body bore. Pattern of holes have been drilled around it
Sleeve
Seated inside the hollow sleeve
Slide
Pressure that is obtained from the pressure port
Bleed pressure
to control bleed pressure is the function of
To opposed solenoid
Metal core, That is placed in the hollow center of the solenoid
Plunger
Directly under the plunger
Plunger pin
Located directly below each plunger pin
Ball
One solenoid has been removed and a pug is installed in the solenoid cavity, one coil spring has been removed and an extended in Has been put in its place, and a double spring has been installed on the opposite end of the slide
Three-way, two position
To convert hydraulic pressure into linear mechanical motion
Hydraulic actuating cylinders
One in which fluid pressure may be directed to only one side of the piston
Double acting unbalanced
Piston rod extending through the piston and out through both ends of the cylinder
Double acting balanced
Inspect for signs of leakage, and take corrective actions, X ternal leakage is the most common trouble encountered
Maintenance
To convert hydraulic pressure into Rotary mechanical motion. The direction of the rotation is controlled by selector valve
Hydraulic motors
